In the piping industry, the mere mention of dissimilar metals is terrifying. Dissimilar metal corrosion can destroy pipes, weaken pipe supports, and cause piping to collapse. Worse yet, once corrosion starts, it can spread throughout your entire piping system.
However, there’s a way to cut off dissimilar metal corrosion before it sets in: pipe isolation. By separating those metals that don’t get along, you can protect your pipes and promote a longer-lasting piping system.
Wondering how to isolate dissimilar metals?
Read on. We’ve laid out five proven ways to isolate dissimilar metals and strengthen your piping system.
Why Isolate Dissimilar Metals?
Dissimilar metals are metals that have significantly different properties. When they come in contact with each other, these metals set off a reaction that eats away metal. Dissimilar metals can create galvanic corrosion—a process through which a noble metal pulls electrons away from a base, active metal. The result is iron oxide, or rust, and weakened metal.
When metal is corroded, it can damage your entire piping system. It puts your system in danger of pipe failures, collapse, on-site disasters, and shutdowns. That’s why it is important to isolate dissimilar metals and keep them from causing galvanic corrosion.
How Does Dissimilar Metal Corrosion Work?
Dissimilar metal corrosion or galvanic corrosion is a reaction that takes place when you pair up an anode and cathode. A common example is when you pair carbon steel with stainless steel. When these two common metals are combined and an electrolyte is introduced, electrons move from your active metal (carbon steel) into the noble metal (stainless steel).
Your carbon steel can rust and crumble. The same process can take place between your pipes and surrounding metals if they hold dissimilar properties.
How to Isolate Dissimilar Metals
By isolating dissimilar metals, you stop galvanic corrosion from starting and protect your piping system. Here are 5 key ways to isolate dissimilar metals and lengthen the lifespan of your piping system:
1. Galvanize Metal
One way to protect dissimilar metals without adding large nonmetallic barriers is to galvanize metal. During the galvanization process, you add a layer of zinc to a base metal in order to add corrosion resistance.
Wondering how this zinc solution helps?
Zinc is a base metal, so its electrons are easy targets for noble metals. Basically, when you add a layer of zinc to the more basic of two dissimilar metals, the noble metal will start stealing electrons from the zinc layer rather than attacking your pipe’s or support’s base metal. In addition to being a sacrificial layer, this extra layer also shields the basic metal from scratches or friction wear, protecting it in the long run.
2. Use Liners
In some cases, you can use composite isolators to keep dissimilar metals apart—but what if you want to use a metallic pipe support without galvanizing? You can still retain the benefits of metal pipe supports, without the danger of corrosion, by adding a liner to your support.
Pipe support liners fit between your metallic pipe support and pipe. They’re made of nonmetallic materials and can be fabricated to hold up to extreme heat, severe cold, and chemical exposure.
In addition to separating dissimilar metals, liners can also cushion pipes and reduce surface abrasions. For instance, APP’s VibraTek Liner is built to cushion pipes, dampen pipe vibrations, and help pipes move naturally along their axis. That can stop corrosion cells from springing up out of surface damage—isolating pipes along the way.
One of the biggest advantages of isolating pipes with liners is the variety of materials you can choose from. Here’s a quick look at some popular materials that make up liners:
With teflon liners, you can isolate pipes in harsh conditions. During the manufacturing process, manufacturers can also bond Teflon to pipe supports to provide a barrier between the pipe and support. This material doesn’t delaminate, so it is able to absorb pipe vibrations in various conditions without tearing apart.
Polyurethane liners are built to stay strong in extreme conditions, including high heat. Manufacturers can also fabricate these liners to fight off UV rays. That way, they hold up to heavy sun exposure—and protect themselves against metal-on-metal damage in the process.
One of the biggest advantages of adding liners to pipes is their versatility. Some manufacturers will craft liners out of materials that fit your piping system’s needs and environment. Some additional custom lining materials include:
- Sodium-etched PTSE
3. Elevate Piping
If you need to lift pipes off metal structures, you can use a pipe support to elevate piping. One of the most popular pipe elevators out there is the pipe shoe. Here’s a quick look at different pipe shoes and how they prevent metal-to-metal corrosion:
Composite Pipe Shoes
Composite pipe shoes are made of an extremely durable nonmetallic material. They lift your metal pipes off of surfaces and control movement. These shoes add protection on several levels:
- They separate metals, so you don’t have to worry about dissimilar metals creating galvanic corrosion.
- They protect your pipes from friction erosion. Rather than scraping against harsh metallic surfaces, your pipes slide on a much more giving composite shoe. That prevents breaks and tears, and it stops small holes from forming and harboring corrosion cells.
Metallic Pipe Shoes
Metallic pipe shoes are also a solid option if you want to lift pipes off of a corrosive surface. However, if you want to isolate pipes using metallic shoes, be sure your pipe supports are preventing dissimilar metal corrosion. Here are some options to prevent metal-on-metal damage:
- Make sure your metallic pipe shoes are made of a metal that is compatible with your metal pipes.
- Add a nonmetallic protective liner to your pipe shoes.
- Galvanize your pipes or your pipe shoes.
4. Use Buffers
Buffers or pipe isolators add a physical layer between your pipe and surrounding metals. Here are a few examples of pipe isolators:
Wear pads fit directly to the outer diameter of your pipe surface. They’re made up of a durable nonmetallic material that keeps your metal pipe from contacting surrounding metal surfaces. Because they fit precisely to your pipe, wear pads move with your pipe as it shifts. That way, you’re also protecting your pipe from the surface corrosion that sometimes starts when pipes rub against other metal objects.
Slide plates normally fit under a pipe support to allow smooth movement between the support and the structure it sits on.
5. Add Hangers
Hangers let you string up pipes and suspend them in the air. That way, they’re not resting on dissimilar metal surfaces or corrosive grime. For instance, you can use clevis hangers to raise pipes off the ground and keep runs off of dissimilar metals.
However, if you’re concerned about dissimilar metal corrosion, you’ll want your hangers to be resistant to corrosion as well. To accomplish this, make sure they’re made of a corrosion-resistant material, such as stainless steel or galvanized steel.
Discover the Secrets to Protecting Your Piping
Want to find the best way to protect your pipes against galvanic corrosion? Start by learning everything you can about galvanizing. Read our free guide The Expert's Guide to Hot-Dip Galvanization to discover the most effective anti-corrosion option for your pipe system.